The present invention relates to communication networks. More particularly, the present invention relates to broadband communication networks having intelligent network control.
Human beings provided the first "intelligence" in the United States telephone network. Rows of human telephone operators, sitting side by side, plugged cords into jacks to handle calls. The operators established calls to distant locations, selected the best routes, and provided billing information. In the 1920s, sophisticated electromechanical switching systems were introduced which allowed automatic switching of telephone calls. Initially, these switching systems served as aids to operators. Ultimately, however, they led to the replacement of operators.
Another significant change to the United States telephone network took place in the mid 1960s, with the implementation of the first stored-program control switch. Switching software in the stored-program control switch enabled a family of custom calling services, e.g., speed calling, call waiting, call forwarding, and three-way calling and a set of Centrex features, e.g., station attendant, call transfer, abbreviated dialing, etc. The first programs for the stored-program control switches contained approximately 100,000 lines of code. By 1990, however, some of the switching systems became enormously complex, containing 10 million lines of code and offering hundreds of different services to telephone users. Because there are over 15,000 switches in the United States telephone network and many different switch types, it is difficult to introduce new services with ubiquity and with service uniformity. For example, it required over twenty years to introduce custom calling services throughout the United States and those services behave differently in different switch types.
In the 1980s, industry applied a new architectural concept to the public switched telephone network (PSTN) to create an Intelligent Network (IN) with which new services could be rapidly deployed with ubiquity and with service uniformity. The availability of features and services in the IN is not dependent solely upon the hardware and software in stored-program control switches. Instead, intelligence is provided in a central data base and accessed using packet switching techniques.
The basic elements of the IN architecture are a switching system, a common channel signaling network, a central data base, and an operations support system. When a customer places a telephone call that requires special handling, such as a toll-free call (800 service) or a credit card call, the call is routed to a service switching point (SSP), which launches a query through a common channel signaling network (CCSN) to a central data base. The central data base, in turn, retrieves information necessary to handle the call and returns that information through the CCSN to the switch. The switch uses the information to complete the call. The central data base is supported by an operations support system, which administers the appropriate network and customer information residing in the data base.
SSPs are stored-program control switches, which interface with the CCSN using the SS7 protocol and 56 kb/s links. SSPs contain the service logic required to intercept calls that require special handling and send queries through the CCSN to centralized data bases to obtain the required call handling information.
The IN also includes the CCSN, which is made up of signal transfer points (STPs). STPs are high-capacity and reliable packet switches for transporting messages between network nodes, such as switches and service control points (SCPs). STPs are typically deployed in pairs with the two members of the pair distant from each other so that a natural disaster at the site of one STP will likely not affect the STP at the other site. STPs also terminate a large number of signaling links, perform protocol processing, and route a high volume of messages through their links. To perform these functions, they require a large routing data base containing translation data.
SCPs, which are also usually paired, provide on-line call handling information in response to network queries. They operate in real-time, with typical response times of less than half a second and have a high availability, with typical down-times of less than three minutes-per-year for an SCP pair.
As explained in more detail below, SCPs contain a set of front-end processors used to perform portions of the SS7 protocol processing, such as the message transfer part (MTP) and the signaling connection control part (SCCP). Using a dual-Ethernet configuration, the front-end processors communicate with a collection of central processing units (CPUs) in the back end. The back-end CPUs process an SS7 application layer protocol called the transaction capabilities application part (TCAP), and essentially perform query processing.
SCPs interface with STPs using a plurality of 56 kb/s SS7 links. They also interface with operations support systems using duplicated 9.6 kb/s X.25links.
For more information on the SCP, reference is made to U.S. Pat. No. 5,084,816, entitled "Real Time Fault Tolerant Transaction Processing System," the contents of which is incorporated by reference.
Finally, the IN includes service management systems (SMSs). An SMS is an interactive operations support system, which processes and updates customer records. It provides an interface between the customer and the centralized data bases in the IN.
FIG. 1A illustrates a circuit-switched intelligent network (IN) 122. The IN 122 includes a LATA 124, a common channel signaling network 136, an SCP 134, and an SMS 135.
The LATA 124 includes a service switching point (SSP) 126 and a plurality of local exchange switches 128 (only one shown). Telephone lines 130 (only one shown) connect customers to the local switches 128. A plurality of interexchange carrier links 132 connect the LATA 124 to other LATAs (not shown). As described above, network services are controlled by the SCP 134, which is supported by an SMS 135. CCSN 136 interfaces the SCP 134 to the SSP 126.
Generally, requests for network services are generated by the SSP 126 when certain events occur while processing a call, e.g. the SSP 126 may launch a query to the SCP 134 when a customer goes off hook or after the customer completes dialing. To handle the queries and responses, the CCSN 136 uses the SS7 protocol which supports TCAP messages between the SSPs and the SCPs. Data links operating at 56 Kb/s are used throughout the signaling network and query response times as seen by the SSP are typically one-half second or more. Unfortunately, the CCSN 136 handles service-related queries and responses at a data transfer rate that is considered unacceptably slow for broadband networks, and does not interface with fast-packet switches.
The Advanced Intelligent Network (AIN) is similar to the IN, as shown for example in FIG. 1B. AIN introduces a service creation capability that allows rapid development of new services and customization of services. It also broadens the participation in service creation in that telephone company personnel as well as their customers can create new services. In the AIN 138 of FIG. 1B, the SPACE.TM. service creation system 146 interfaces with the ISCP 144. The ISCP 144 is interfaced to STPs 140 and 142, which are part of the CCSN. STPs 140 and 142 are connected to an SSP 147 in the circuit-switched network. The SPACE system provides the capability for automatically programming the ISCP to execute new network services.
The IN and AIN support a variety of existing telephone voice services, one example being alternate billing services (ABSs). ABSs include a calling card service, collect call service, and bill-to-third number service. In accordance with the ABS architecture, a call is routed to an operator services system (OSS), which launches a query through an SS7 CCSN to an SCP. The SCP provides routing information, such as the identity of the customer-specified carrier that is to handle the call, as well as screening functions, such as validating a calling card. The SCP returns the appropriate information to the inquiring OSS, which completes the call.
Another example of an existing voice service is an 800 toll-free calling service. This service enables a subscriber to use a single 800 number with different carriers. 800 number calls are routed to an SSP, which launches queries through an SS7 CCSN to an SCP. The SCP identifies the appropriate carrier, as specified by the 800 service subscriber, and, if appropriate, translates the 800 directory number to a plain old telephone service (POTS) number. The SCP returns this information to the SSP, which hands the call off to the appropriate carrier. This technology allows customers to select the carrier and the POTS directory number as a function of criteria such as time-of-day, day-of-week, percent allocation, and location of the calling station.
With the use of special software, SCPs can also give the PSTN the characteristics of a private virtual network (PVN). With the IN architecture that supports PVN, the SCP data base can provide screening, routing, and billing functions. A PVN serves a closed user group, and a caller requires authorization to get on the network. Thus, the PVN screens calls for those that can access the network based on the directory number of the calling party or based on an authorization code. The validation or authorization function is similar to that implemented for ABSs when calling cards are validated. The PVN also offers an abbreviated dialing plan. In this case, the SCP translates an address and converts an abbreviated set of digits, e.g., four digits, seven digits, etc., to a 10-digit POTS number. This is analogous to the 800-to-POTS translation associated with 800 service. The PVN may also provide additional customer-specified routing functions, which involve selections from a hierarchy of facilities, such that when all circuits in one facility are busy, traffic is routed over an alternate facility. Finally, the PVN may perform a billing function when different charges exist, depending upon the facilities it uses for routing.
The IN and AIN can also support some data services. For example, a customer may connect a data terminal or computer to the network and communicate with another data terminal or computer. To support these services, the front-end of an SCP is enhanced, allowing it to communicate with a data signaling network, such as the X.25 network. With this enhancement, many of the services traditionally associated with voice customers, such as 800 service, ABS, or PVN Service, can be deployed for data customers. For example, an ABS for data customers allows data calls to be placed using the same calling card and calling card number used for voice calls. In this instance, the SCP accepts X.25 queries from a packet switch that functions relatively slowly in a public packet-switched network (PPSN), instead of SS7 queries from an operator services system in a circuit-switched network.
While the IN and AIN can be used to meet some voice and data needs of customers, they cannot meet customer's needs for broadband video and data services because the underlying circuit-switched network is limited by its bandwidth and signaling speeds.
Fast-packet switching technology is being developed for broadband networks with voice, high-speed data, and video transmission capabilities. However, these networks are quite limited and lack the intelligence and flexibility to support many services. Evolving architectures for broadband networks employ fast-packet switches interconnected through fiber-optic facilities. The fast-packet switches make permanent or "nailed up" virtual connections for subscriber calls. Although these permanent virtual connections have application, for example, in limited private networks, such connections have little use in intelligent telecommunication networks because they are inflexible.
In sum, fast-packet switches lack embedded intelligence for practical network-based services. Also, intelligent network controls, which exist in today's circuit-switched networks, for example, the IN and AIN, which employ relatively slow common channel signaling systems, are not satisfactory for fast-packet switches.